1. Field of the Invention
The invention relates to flavoured food products and processes for their preparation. In particular it relates to food products containing certain precursors of flavouring agents having a thiol group which can be represented by the general formula R.sup.1 --SH, in which R.sup.1 represents an optionally substituted alkyl, aryl or heterocyclic radical.
By precursors of flavouring agents are to be understood compounds which yield the flavouring agents when the food products at issue are being manufactured, stored or prepared for consumption. In the present case, preferably the last possibility is aimed at.
2. The Prior Art
Many classes of flavouring agents having a thiol group in their molecule are known. Examples are the alkanethiols such as methanethiol, ethanethiol, 1-propanethiol, and butanethiols, substituted alkanethiols such as 1-hydroxypropane-3-thiol, (2-furyl)-methanethiol, aromatic thiols such as benzenethiol, 2-hydroxythiophenol and methylbenzenethiols. Alkylthioalkanethiols, such as 1-methylthioethanethiol, 1-methylthiopropanethiol, 1-ethylthioethanethiol and 1-ethylthiopropanethiol, have been disclosed in Tetrahedron Letters, pp. 2321-2322, Pergamon Press, 1971.
Heterocyclic mercapto compounds, more particularly those having a furane or thiophene structure, such as e.g. 2,5-dimethylfuran-3-thiol, 2,5-dimethyl-4,5-dihydrofuran-3-thiol, 2-methyltetrahydrofuran-3-thiol, have been disclosed in Dutch patent application No. 6,910,103.
The flavouring agents containing a mercapto group have suitable flavours for various applications. However, they suffer sometimes from instability; they may convert into compounds with no or undesirable flavouring properties. These thiols may e.g. oxidize to disulphides, having different flavours, if at all, which may occur during processing, storage or preparation. These, and e.g. losses due to vaporization of flavour compounds, may necessitate the incorporation of relatively high initial quantities of the desired flavouring thiols in the food products in order to have the correct amount available in the foodstuff which is ready for consumption.